INFLUENCE OF CHEMICAL-CHANGES OF THE ISOTROPIC MATRIX ON PHYSICAL-PROPERTIES OF MESOPHASE PITCH

The temperature dependence of average molecular mass and carbon conten t of the isotropic matrix prepared by heat treatment of coal tar pitch exhibits distinct local minima at 400 degrees C. This temperature agr ees approximately with the position of local extremes on viscosity cur ves, designated as maximum/minimum. The anomalies were attributed to a ccelerated mesophase formation affecting the chemical and theological properties of the isotropic matrix. For this study samples of mesophas e pitch were prepared at 250, 300, 350, 400 and 450 degrees C. After r emoval of anisotropic QI substances by extraction with quinoline the p ortions of isotropic matrix were further separated by solvent fraction ation into groups of maltenes, asphaltenes plus preasphaltenes (APA) a nd carboids (CA). The soluble samples of APA and CA have been obtained by means of non-reductive alkylation. Their 'average molecule' was ch aracterized by elemental composition, n.m.r. spectroscopy and vapour o smometry.